<pre><?php
define('ROOT_PATH',	realpath(dirname(__FILE__) . '/../'));

// xml content
$xmlString	= file_get_contents(ROOT_PATH . '/resource/OpenDocument-schema-v1.1.rng');

// prepare namespace for simple xml
$xmlString	= str_replace('xmlns=', 'ns=', $xmlString);
$xml		= simplexml_load_string($xmlString);

$defines	= $xml->xpath('define');

var_dump($defines);